Ruby: replace hash value with value from another hash

Question

I can't seem to figure this one out. If I have two hashes, where a value in the first hash should always match a key in the 2nd hash:

hash1 = { :table => 'name', :action => 'view' }
hash2 = { 'name'  => 'first_name', 'group'   => 'user_group' }

The key :table is a constant, but the value is dynamic. How can I swap the value in hash1 with the value in hash2, where the key matches the value in hash1? Without knowing what the actual key or value will be (other than :table in hash1)? Hope that makes sense, the updated hash1 (or new hash) should look like this:

hash1 = { :table => 'first_name', :action => 'view' }

Thanks in advance.

I don't see any code showing you tried to solve this yourself. — the Tin Man
– the Tin Man, Commented Jul 22, 2013 at 13:47

sawa · Accepted Answer · 2013-07-22 13:46:26Z

1

hash1.each{|k, v| hash1[k] = hash2[v] if hash2.key?(v)}

answered Jul 22, 2013 at 13:46

sawa

169k51 gold badges287 silver badges398 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

tokland · Accepted Answer · 2013-07-22 14:24:11Z

1

I'd write (non-destructive):

hash3 = Hash[hash1.map { |k, v| [k, hash2.fetch(v, v)] }]
#=> {:table=>"first_name", :action=>"view"}

edited Jul 22, 2013 at 14:24

answered Jul 22, 2013 at 14:00

tokland

68.2k13 gold badges151 silver badges174 bronze badges

3 Comments

sawa Over a year ago

I don't know if the OP really intended this, but the question is asking to destructively modify hash1.

sawa Over a year ago

What was wrong with your fetch? I thought it was nice. And now, you need to assume that hash2 does not include a nil or falue value.

tokland Over a year ago

@sawa: there you go, fetch again. I cannot seem to make up my mind whether I prefer [k] || v or h.fetch(k, v).

Arup Rakshit · Accepted Answer · 2013-07-22 13:49:14Z

0

hash1 = { :table => 'name', :action => 'view' }
hash2 = { 'name'  => 'first_name', 'group'   => 'user_group' }

hash2.each{|k,v| hash1[hash1.key(k)] = v if hash1.has_value? k}
p hash1
# >> {:table=>"first_name", :action=>"view"}

answered Jul 22, 2013 at 13:49

Arup Rakshit

119k30 gold badges270 silver badges328 bronze badges

Collectives™ on Stack Overflow

Ruby: replace hash value with value from another hash

3 Answers 3

Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related